Nanosized carbonaceous material three-dimensional structure and process for producing the same

ABSTRACT

According to the present invention, there are provided a novel graphite-like three-dimensional structure which has a partial structure bent-up with such a steeper curvature than that observed for a carbonaceous material having a conventional nanosize three-dimensional structure such as fullerene and nanotube, has such a feature as light weight and high mechanical strength, as well as a process for manufacturing the same. In the present invention, under a high temperature and a low pressure, a plurality of nanosize graphite layer fragments are forced to coming into collision at a high speed in a relative orientation where the layer planes are not set in parallel to form a carbonaceous three-dimensional structure where at least a plurality of graphite-layer-like layer planes having a hexagonal network structure made up of carbon are arranged such that they mutually cross or are in contact with each other and at the sites for the contact between the plurality of layer planes, connections via carbon-carbon covalent bonds are aligned in the shape of a cross-line.

TECHNICAL FIELD

The present invention relates to a carbonaceous materialthree-dimensional structure having a nanosized three-dimensionalstructure and a producing process therefor. In particular, it relates toa carbonaceous material three-dimensional structure where said nanosizedthree-dimensional structure is a three-dimensional structure constructedby combining a plurality of graphite-layer-like layered parts having ahexagonal network structure made up of carbon as well as a process forforming the three-dimensional structure.

BACKGROUND ART

There have been recently reported, in addition to a finethree-dimensional structure made up of single-layer wall such assingle-layer carbon nanotube, a graphite-layer like multi-layeredsubstance composed of a plurality of graphite-layer-like structures, asfor a carbonaceous material having a fine structure in nanoscale. Forinstance, known examples of such a structure include a three-dimensionalstructure where multiple fine graphite layers are stacked up in adirection of a graphite c-axis; a multi-layer carbon nanotube or onionstructure where multiple graphite layers are lapped over in the form ofcurved surface. A gas-absorbing surface structure in charcoal is alsomicroscopically a type of fine structure where a plurality of graphitelayers is piled up.

For example, in a nanosize carbonaceous material three-dimensionalstructure composed of curved graphite layers, the curved surface of thegraphite layer functions as a site for adsorbing molecules or atoms andhas a higher ratio of surface area per a unit volume. Therefore, thereis increased progress for its use as a physical adsorbent for gaseousmolecules or atoms.

DISCLOSURE OF INVENTION

In terms of a fine three-dimensional structure made of a carbonaceousmaterial, there has been looked forward to proposal of a novelcarbonaceous material three-dimensional structure showing having such ananosize steric structure that it shows structural form other than afine three-dimensional structure made up of single-layer wall or a finestructure composed of stacked-up multiple graphite layers which has beenpreviously reported, and it has a higher potential for light-weight andcomparable or higher mechanical strength in comparison with aconventional carbonaceous material of multi-layered structure type. Inparticular, there has been needed to develop a new carbonaceous materialthree-dimensional structure having a structural form that is quitedifferent from that of a conventional carbonaceous material having ananosize fine three-dimensional structure, which can show stablefunctions under severe conditions (under a high temperature or a strainfield) to be adapted to wide spectra of application such as amolecule/atom adsorbing structure, a material used in an electronicdevice or a material with persistence.

For solving the above problems, an objective of the present invention isto provide a carbonaceous material three-dimensional structure having anovel three-dimensional structure which can function stably under severeconditions (under a high temperature or a strain field) so as to be fitto a wide variety of applications such as a molecule/atom adsorbingstructure, material for an electron device and material withpersistence, as well as a process for the production thereof.

We made an extensive study with the view of solving the above problems,and we have obtained the following findings: For example, Laserevaporation of a material of graphite form such as graphite by means oflaser abrasion method provides formation of a number of fine graphitepieces having a graphite-layer-like hexagonal network structure made upof carbon. When the resultant fine graphite pieces are condensatedagain, they are stacked up in layered form to reconstruct multi-layeredgraphite therefrom, and further, in such a case where a plurality offine graphite pieces may occasionally come into contact with each otherat inter-plane angle being non-parallel, a new carbon-carbon covalentbond is formed just at the site in contact, resulting in the productionof a nanosize three-dimensional structure in which two or moregraphite-layer-like hexagonal network structures made up of carbons arearranged at inter-plane angle being non-parallel to each other. Inaddition, in said nanosize three-dimensional structure where two or moregraphite-layer-like hexagonal network structures made up of carbons aredisposed at the inter-plane angle being non-parallel therebetween, amutual arrangement of hexagonal network structures made up ofgraphite-layer-like carbon is determined by the carbon-carbon covalentbonds, is reliably maintained under severe conditions (for instance,under a high temperature and a strain field being initiated) andexhibits sufficiently high mechanical strength. Thus, based on thosefinding, we have completed the present invention.

That is to said, a carbonaceous three-dimensional structure that isprovided according to an aspect of the present invention is

a carbonaceous three-dimensional structure which is a three-dimensionalstructure made of carbonaceous material comprising a plurality ofgraphite-layer-like layer planes that are composed of a hexagonalnetwork structure made up of carbon, wherein

the plurality of graphite-layer-like layer planes are arranged such thatthey mutually intersect or are in contact with each other; and

at the sites for the contact between the plurality of layer planes,there are aligned connections via carbon-carbon covalent bonds in theshape of a cross-line. In such a case, it may be, for instance, athree-dimensional structure wherein the cross-line formed at the sitesfor the contact between the plurality of layer planes where there arealigned connections via carbon-carbon covalent bonds constructs astraight or curved line.

Further, preferred is the three-dimensional structure wherein as thesites for the contact between the plurality of layer planes where thereare aligned connections via carbon-carbon covalent bonds, there is atleast one structure where three or more surfaces of thegraphite-layer-like layer planes are arranged so as to mutuallyintersect or are in contact with each other on the same cross-line.

Alternatively, a carbonaceous three-dimensional structure that isprovided according to another aspect of the present invention is

a carbonaceous three-dimensional structure which is a three-dimensionalstructure made of carbonaceous material comprising a plurality ofgraphite-layer-like layer planes that are composed of a hexagonalnetwork structure made up of carbon, wherein

the at least two graphite-layer-like layer planes are non-parallelgraphite layer planes and have such a structure that the site for thecontact therebetween forms a straight crease. In such a case, forexample, it may be a tree-dimensional structure wherein among theplurality of graphite-layer-like layer planes including the at least twographite-layer-like layer planes of which the site for the contact formsa straight crease, the at least two graphite-layer-like layer planesforming the straight crease and at least one additionalgraphite-layer-like layer plane have such a configuration as to mutuallycross or be in contact with each other on the same cross-line.

Furthermore, in the carbonaceous three-dimensional structure accordingto the present invention, there may be provided

a carbonaceous three-dimensional structure which is a three-dimensionalstructure made of carbonaceous material comprising a plurality ofgraphite-layer-like layer planes that are composed of a hexagonalnetwork structure made up of carbon, wherein

the structure comprises at least a frame composed of some of or all ofthe three-dimensional structures, which are given by the carbonaceousthree-dimensional structures with the aforementioned constitutions ofthe present inventions, concurring in compositive manner.

In addition, a method for using a carbonaceous three-dimensionalstructure that is provided according to one aspect of the presentinvention is

a method of using any one of the carbonaceous three-dimensionalstructures with the aforementioned constitutions of the presentinventions, wherein

the carbonaceous three-dimensional structure is used to form amolecule/atom adsorbing material.

Alternatively, a method for using a carbonaceous three-dimensionalstructure that is provided according to another aspect of the presentinvention is

a method of using any one of the carbonaceous three-dimensionalstructures with the aforementioned constitutions of the presentinventions, wherein

the carbonaceous three-dimensional structure is used to form anelectronic device having at least three terminals. In such a case, forexample, the electronic device having at least three terminals may be atransistor.

Further, a method for using a carbonaceous three-dimensional structurethat is provided according to another aspect of the present invention is

a method for using any one of the carbonaceous three-dimensionalstructures with the aforementioned constitutions of the presentinventions, wherein

the carbonaceous three-dimensional structure is used to form areinforcing material.

Besides, the present invention also provides a process for manufacturingthe aforementioned carbonaceous three-dimensional structure of thepresent invention. That is, a process for manufacturing a carbonaceousmaterial three-dimensional structure according to the present inventionis

a process for constructing a carbonaceous three-dimensional structure,which process is process for constructing a three-dimensional structuremade of carbonaceous material comprising a plurality ofgraphite-layer-like layer planes that are composed of a hexagonalnetwork structure made up of carbon, wherein

said three-dimensional structure is any one of the carbonaceousthree-dimensional structures having the aforementioned constitutionsaccording to the present invention; and

the process comprises step of:

producing graphite-layer-like fragments having a hexagonal networkstructure made of carbon; and

forcing the graphite-layer-like fragments produced thereby into cominginto collision with each other. In such a case, it is preferable that inthe step of forcing the graphite-layer-like fragments,

at least two fragments are impacted to each other in an arrangement thatthe fragments mutually cross or are in contact with each other at aninter-plane angle between the graphite-layer-like fragments to be incollision showing substantially other than 180°.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration schematically showing an example of a processfor forming a three-dimensional structure of carbonaceous materialaccording to the present invention.

FIG. 2 is a schematic view illustrating an example of an electronicdevice constructed by using a three-dimensional structure ofcarbonaceous material according to the present invention, explaining athree-terminal type electronic device configuration having such a set-upthat three graphite layer planes contact on the same straightcross-line, in which configuration the cross-line portion acts as apotential barrier to a path between terminal 1 (the first terminal:source electrode terminal) and terminal 2 (the second terminal: drainelectrode terminal) for current flowing across the cross-line portion,and a control voltage is applied to terminal 3 (the third terminal:gate) via a gate electrode (gate electrode unit) 4 to control thedensity of the current passing through the potential barrier in thecross-line.

FIG. 3 is a schematic view illustrating an example of a molecule/atomadsorbing material that is formed by using a three-dimensional structureof carbonaceous material according to the present invention, where threegraphite layer planes contact on the same straight cross-line andwhereby it fulfils a function of physically adsorbing molecules/atoms(adsorbed gas species 5) due to an adsorbing sites in the vicinity ofthe cross-line.

FIG. 4 is a schematic view showing an example of a reinforcing materialthat is formed by using a three-dimensional structure of carbonaceousmaterial according to the present invention, where a plurality ofpartial structures, in which three graphite layer planes are in contacton the same straight cross-line, are joined up, and thereby as a whole,the structure is given with good performance for keeping mechanicalstrength resulting from the a honeycomb structure.

BEST MODE FOR CARRYING OUT THE INVENTION

A carbonaceous three-dimensional structure according to the presentinvention has a three-dimensional structure where a wall plane havinggraphite layer type hexagonal network structure cross-links with anothergraphite-layer-like plane having hexagonal network structure from anoff-plane direction to the wall plane, in contrast with a frame such asa single-layer carbon nanotube and a nanohorn structure in whichgraphite layer type hexagonal network structure walls are joinedtogether within a layer plane to compose such a structure constitutedwith curved plane having a given curvature as a whole. Morespecifically, as illustrated in FIG. 1, it is corresponding to such astructure formed by the process wherein, to a first plane having agraphite layer type hexagonal network structure, another plane ofgraphite-layer-like plane gets closer from an off-plane direction sothat dangling bonds of carbon atoms present in the plane ends act on thecarbon atoms located within the plane of the other graphite-layer-likeplane, whereby new carbon-carbon bonding is formed between those twocarbon atoms to convert it into an integrated three-dimensionalstructure. As shown in FIG. 1, as the connections through formation ofcarbon-carbon bonding between these are aligned adjacently, the sitesfor cross-linking come in a continued cross-line.

The in-plane carbon atom to which a new carbon-carbon bond has beenformed in an off-plane direction has now four bonds in total, that is,the newly formed bond in addition to originally formed bonds betweenthree adjacent carbon atoms in the same plane. Finally, joint betweentwo graphite layers is completed to convert them into such a shape thatthree graphite layer planes with different planar orientation are joinedtogether via a carbon atom having a sp³ type hybrid orbital at the sitesof the cross-line. Although it is very often that the sites of thecross-line are at least partially aligned in a line, the layer planeitself of the graphite layers forming the cross-line may, as a whole,optionally exhibit a shape being curved with a small curvature ratherthan planar form, and thus the sites of the cross-lines may come in acurve as a whole.

As described above, in the three-dimensional structure produced throughthe process for forming a connection between two graphite layers, astraight crease is formed at the sites for the cross-line to devide onegraphite layer into two graphite-layer-like planes. Furthermore, agraphite layer initially involved in forming a bond from an off-planardirection is set up as a graphite layer plane not parallel to at leastthe adjacent graphite-layer-like plane after completing the bondforming, as shown in FIG. 1, and thereby such a structure in which thesites for the contact forms a straight crease is built up.

Furthermore, it is possible to form a composite three-dimensionalstructure where a plurality of said three-dimensional structures havingthe above straight crease are mutually joined. For example, as shown inFIG. 4, there may be formed a honeycomb structure which includes thethree-dimensional structures having a straight crease as its ridgelines.In the composite three-dimensional structure as shown in FIG. 4, theridgelines for each inner cell thereof are formed in such a shape thatthree graphite-layer-like planes are intersected to join with each otheron a straight cross-line, while the outer ridgelines for the outermostcells have such a shape that two graphite-layer-like planes are mutuallycross-linked to produce a straight crease. Thus, there is formed acomposite three-dimensional structure having at least two differenttypes of ridgeline shapes.

For example, in the composite three-dimensional structure shown in FIG.4, when applying an external compressing or stretching force in thedirection along to the ridgeline of its honeycomb structure, thegraphite layers employed as a wall for the honeycomb structure showhigher resistance to compression or stretching stress in an in-planedirection, and significantly higher mechanical strength in thisdirection owing to stress-decentralizing effect of the honeycombstructure itself. On the other hand, to lateral deformation distorting acell of the above honeycomb structure, a nanosize graphite layer canallow slight flexion and can, as a whole, decentralize deformation toexhibit flexibility to a certain degree. However, for crushing the wholehoneycomb structure, it is necessary either to crack a graphite layeritself to pieces that composes a wall of each cell or to break theconnections via a carbon atom having a sp³ type hybrid orbital whichform a ridgeline of the honeycomb structure. Thus the structure exhibitsresistance to a significant external stress load. Therefore, theproperty of the structure such that it can flexibly respond todeformation in an in-plane direction, that is, it can be elasticallydeformed, while it exhibit significant robustness to an external forcein a direction perpendicular to the plane, particularly a compressingforce, is suitable for forming a reinforcing material that isappropriate to a coating material.

The above-mentioned mechanical strength is originated from such afeature that as in the carbonaceous three-dimensional structureaccording to the present invention, a plurality of graphite-layer-likeplanes are arranged so as to intersect or be in contact with each otheron one cross-line and are joined together by formation of carbon-carbonbonds therebetween, a stress for compressing or stretching strain thatis impressed along to the direction of the cross-line can be dispersedin the plurality of graphite-layer-like planes being cross-linked on thecross-line, and flexure within each graphite layer plane is suppressed,so that the structure can exhibit higher resistance as a whole. Herein,although a cell structure similar to a honeycomb structure is a morepreferable form, at least, a three-dimensional structure containing atleast one configuration where three or more graphite-layer-like layerplanes are arranged so as to mutually intersect or be in contact witheach other on the same cross-line, or alternatively, a three-dimensionalstructure having a configuration where at least two graphite-layer-likelayer planes are non-parallel graphite layer plane so that the sites forthe contact thereof form a straight crease may be, in general, acarbonaceous three-dimensional structure exhibiting much highermechanical strength per a unit weight than that of the structure wherethe same number of graphite layers are simply stacked up in parallel.

In the three-dimensional structure of carbonaceous material according tothe present invention, when such a configuration where a plurality ofgraphite layers intersect or are in contact with each other is set up, across angle between two graphite layer planes comes, for example, to120° for that shown in FIG. 1, and thus near the cross-line for thejoining portion, a plane orientation will show drastically change. Inother words, near the cross-line for the joining portion, a surfaceπ-electron state is present in the manner equivalent to a case where agraphite layer plane is curved with a large curvature. As illustrated inFIG. 3, as a local curvature in such a portion for the contact isremarkably larger than the curvature in a curved graphite layer in ananotube or an onion structure, an effective contact area thereof isincreased in a physical adsorption process of molecules/atoms.Therefore, there are formed physical adsorption sites having strongadsorbing properties in the vicinity of the cross-line of thecross-linking portion. Thus, the structure can be applied to amolecule/atom adsorbing functional material. Specifically, it can beused as an adsorbing material for fuel gas molecules such as methane orethane. In such a case, by constructing a three-dimensional structurewhere the cross-linking portions are two-dimensionally gathered as shownin FIG. 4, there can be provided a molecule/atom adsorbing materialhaving a great improvement in the number of adsorbed gas molecules per aunit weight.

As shown in FIG. 1, connection is formed between two graphite layerplanes to come in the shape where three graphite layer planes havingdifferent plane orientations are joined together in its cross-line via acarbon atom having a sp³ type hybrid orbital, and thereby a π-electronconjugation system within the graphite layer plane is interrupted in thecross-line. Specifically, on the cross-line, a chemical bond angle of acentral carbon atom having a sp³ type hybrid orbital to an adjacentcarbon atom is close to 109.5° of that for diamond. A plurality of suchcentral carbons having a sp³ type hybrid orbital are continuouslypresent on the cross-line. When a width of a graphite layer forming thecross-line as shown in FIG. 2 reaches about 100 nm, 50 or more carbonatoms are present on the cross-line, so that a fine region having atwo-dimensional band structure derived from the above translationalsymmetry is formed therein. In such a case, a local bandgap formed inthe fine region may occasionally reach up to about 1 eV.

Accordingly, in the three-dimensional structure where three graphitelayer portions form carbon-carbon bonds in the cross-line as shown inFIG. 2, such a configuration that a microscopic barrier region having adifferent local bandgap in the cross-line is joined to a two-dimensionalπ-electron conjugation system type of band structure in each graphitelayer portion is made up. That is to say, a current path from graphiteterminal 1 to terminal 2 (or from 1 to 3, or from 2 to 3) in FIG. 2 isset up in such a form that a tunnel current passes through themicroscopic barrier region in the cross-line. For example, in the casewhen a tunnel current is allowed to flow from terminal 1 to terminal 2by applying a bias, the increased tunnel current can be induced byapplying an electric field in a direction such that a potential isgradually reduced from the central cross-line to terminal 3. Inoccasion, such a three-terminal type electronic device may haveproperties equivalent to transistor operation. In such a case, when thelocal bandgap built up in the microscopic barrier region in thecross-line is about 1 eV, the increased tunnel current can be adequatelycaused by setting up a potential difference that is due to an externallyapplied electric field to about 1 eV. In practice, when the localbandgap built up in the microscopic barrier region is about 1 eV,induced change in a potential difference only by 1 eV or less may leadto 10- or more folds of change in a density of current passing throughthe barrier region. On the other hand, in the case when a width of thegraphite layer forming the cross-line is about 100 nm, an absolute valueof said current at the on-state of the operation is only in several μA.Thus, power consumption for the resultant transistor is of lower levelin proportional thereto.

For example, in the case when forming a transistor utilizing thenanosize carbonaceous three-dimensional structure as illustrated in FIG.2, if graphite layer terminals 1 and 2 are set as source and drainelectrodes, respectively, the microscopic barrier region in thecross-line is influenced by the electric line of force due to gateelectrode 4 via the graphite layer terminal 3, resulting in modulationof the amount of a current passing from terminal 1 to terminal 2 throughthe microscopic barrier region built up in the cross-line.

In the three-dimensional structure of carbonaceous material according tothe present invention, in order to put the plurality ofgraphite-layer-like layer planes in such position that they intersect orare in contact with each other, where the portion of contact between theplurality of layer planes are constructed in such a shape thatconnections via carbon-carbon covalent bonds are aligned as across-line, nanosize graphite layer fragments are formed beforehand, andthen the plurality of graphite layer fragments are impacted to eachother to conduct the formation of said carbon-carbon covalent bonds. Atthe step of colliding the graphite layer fragments with each other, ifthe graphite layer fragments coming in collisions are arranged in theorientation parallel to each other, the graphite layer fragments arestacked up in the layered form in the c-axis direction, and re-growthand expansion of the graphite layer progresses within the layer plane.In final, produced therefrom is a layered graphite structure which isthe most stable configuration, or alternatively in the presence of ametal catalyst, a carbon nano-material such as nanotube and fullerene[Reference A: T. Kawai, Y. Miyamoto, O. Sugino, and Y Koga, PhysicalReview B66, p33404 (2002)].

In the manufacturing process according to the present invention, asemployed is such a condition that graphite layer fragments are mutuallycollided at a high speed with a collision angle between the graphitelayer fragments being set at angle substantially other than 180°, suchsituation that from an off-plane direction in one graphite layerfragment, a plane end of another graphite layer fragment comes closewith a given angle takes place. As a carbon atom at the end of thegraphite layer plane has dangling bonds, a covalent bond is formed byusing a π-electron exposed toward an off-plane direction from the carbonatom in the hexagonal network structure in the graphite layer fragmentand an electron from said dangling bond, and whereby the formation of acarbon-carbon bond between two graphite layers can bring about theconstruction of three-dimensional structure as shown in FIG. 1. Thethree-dimensional structure thus obtained is made up in a configurationthat connections via carbon-carbon covalent bonds are aligned as across-line and a plurality of graphite-layer-like layer planes joinedmutually intersect or are in contact with each other.

Therefore, in terms of process for forming graphite layer fragments tobe collided, preferably, a graphite-like material is first exposed tohigh-temperature and high-pressure conditions by laser evaporation.Next, gaseous carbon molecules (fragments) generated therefrom are flownalong with a carrier gas and then rapidly cooled down. Due to the rapidcooing-down step, carbon molecules (fragments) and crashed-up carbonatoms are rapidly aggregated to reconstitute a graphite-like structurelayer, and thereby a large number of small graphite layer fragments areproduced. In addition, during the stage of rapid aggregation, there areoccurred such phenomena that the graphite layer fragments produced comeinto collision with each other at a high speed.

In the manufacturing process according to the present invention, in thecase when said phenomena that the graphite layer fragments produced arein collision at a high speed occur, by giving rise to such a situationthat the graphite layer fragments are impacted to each other at a highspeed with a collision angle being set up to angle substantially otherthan 180°, the production of the novel three-dimensional structure ofthe present invention is achieved.

In the manufacturing process according to the present invention, thereare also produced such a byproduct as a conventional layered structuretype of graphite and carbon nanotube even in small amounts, in additionto the aimed three-dimensional structure of carbonaceous material. Inorder to separate these byproducts from the aimed three-dimensionalstructure of carbonaceous material, less reactive gas molecules with alarge weight such as bromine molecules (Br₂) are introduced to thecarbonaceous material produced. Since the less reactive molecules suchas bromine molecules are preferentially adsorbed on the aimedthree-dimensional structure of carbonaceous material exhibiting higheradsorbing ability, a sample with an increased bulk specific gravity bythe adsorption process can be precipitated in the solution. Theprecipitated substance is collected and then subjected to heat-treatmentat a temperature of several hundred centigrade. The adsorbed moleculeswith a lower bonding affinity can be thus easily removed from the aimedthree-dimensional structure of carbonaceous material. By conducting theabove separation step utilizing a specific-gravity difference, only thethree-dimensional structure of carbonaceous material according to thepresent invention finally remains.

EXAMPLE

The present invention will be more specifically explained with referenceto an example. The specific example is one of the best modes accordingto the present invention, but the present invention is by no meanslimited to the specific modes exemplified.

Example

Under a reduced pressure, graphite evaporated by laser abrasion isconverted into fine fragments having a graphite-like hexagonal networkstructure, which fly out at a high speed. It is well-known that when thegraphite-layer-like fine fragments are re-aggregated by cooling, theycan give a nano-scale structure such as fullerene and nanotube ratherthan multi-layered graphite which is the thermodynamically most stablestructure. In particular, it is well-known that when a catalyst metal isevaporated together with graphite by laser abrasion, a nanotubestructure can be more efficiently produced through re-aggregation withuse of the action of the catalyst metal. When evaporated carbonfragments are aggregated without a catalyst metal, a material called“nanohone” may be synthesized [Reference B: S. Iijima, M. Yudasaka, R.Yamada, S. Bandow, K. Suenaga, F. Kokai, K. Takahashi, Chemical PhysicsLetter, Vol. 309 p. 165-170 (1999)].

Some of the graphite fragments generated by evaporation of graphite bylaser abrasion under high-temperature and low-pressure conditions comeinto collision at a high speed in the orientation being not in parallelbut with a given angle. The high-speed collision between graphitefragments with an angle results in the three-dimensional structure wheregraphite layers are mutually joined in such a shape as illustrated inFIG. 1. In that step, for achieving a high temperature, CO₂ laserirradiation is employed. By controlling a laser power and an irradiationtime during CO₂ laser irradiation, the size of the fragments vaporizedfrom a target graphite and their kinetic energy can be controlled. Inthe manufacturing process according to the present invention, desirablya laser power is 15 KW/cm² to 30 KW/cm², a laser pulse width is 200 msto 700 ms, and a pulse irradiation period (frequency) is 1 s (1 Hz).

The nano-materials synthesized by said process can exist whilemaintaining their metastable three-dimensional structures by the help ofa cooling gas in the chamber (for example, N₂, Ar and Ne). Furthermore,nano-materials having such a three-dimensional elementary structure asshown in FIG. 1 may be further aggregated to compose such a largerthree-dimensional structure as illustrated in FIG. 4. FIG. 4 illustratesa part of three-dimensional elementary structures contained in anaggregated huge structure. Although not shown in FIG. 4, in the end partof the aggregated structure obtained, a graphite layer edge may remainas it is at the end, but a curved graphite layer type of linking-jointis formed such that two adjacent graphite layers at the end areconnected. It may be speculated that the process for forming such acurved joint portion at the end region proceeds in accordance with aphenomenon similar to a mechanism for forming smoothly-connectedgraphite layer planes in a nanotube or nanohorn structure. Furthermore,between a plurality of aggregate structures which are separatelyproduced, linking-joints may be formed during the formation of jointportion in the end region, and thereby further multiplexing may beadvanced occasionally.

A graphite layer itself is chemically inert, but its layer surface hascapability of adsorbing gas molecules with use of a physical adsorptiveaffinity. In order to increase the physical adsorptive affinity to gasmolecules, it is appropriate to make the π-electrons interactingadsorbed molecules chemically active by such a way that a graphite layerplane is distorted from a flat plane to generate a curvature, and aconjugation system of π-electrons spreading in a perpendicular directionto the layer plane is interrupted by the plane distortion. In ananotube, a curvature is generated by one graphite layer constitutingthereof that is wound as a helix. In such a case, the curvature, whichcan be achieved thereby, is inherently limited because it depends on aradius, that is, a helix pitch of the nanotube. In contrast, thethree-dimensional structure according to the present invention is athree-dimensional structure where graphite layers are branched along acentral cross-line as shown in FIG. 1, and a local curvature near thecentral cross-line is quite superior to an averaged curvature infullerene or nanotube. In a curved part having such a steeper angle, aneffective contact area between an adsorbed molecule and a graphite layeris so large that a high adsorbing affinity can be achieved. For example,there is a good chance that it will be successfully applied to anadsorbing material for gas molecules such as methane or ethane that isrequired in a fuel cell. A range where the cross-line as illustrated inFIG. 1 that is applicable to the sites for absorption is formed is fromseveral nanometers to several hundred nanometers.

In the three-dimensional structure shown in FIG. 1, when applying anexternal force from a direction parallel to each graphite layer, adistortion may never be induced so easily as that for one graphitelayer. Such three-dimensional structure units may be two-dimensionallyrepeated to construct a honeycomb structure formed by single-layergraphite walls, so that as the whole three-dimensional structure havinga honeycomb configuration, a material with higher mechanical strengthcan be obtained even though it includes a lot of openings within thecell structure. FIG. 4 illustrates an example of a structure having sucha honeycomb configuration. It has a particularly higher strength alongto the ridgeline direction in the honeycomb structure shown in FIG. 4.On the other hand, it exhibits flexibility to a pressure in a directionperpendicular to the direction of the honeycomb structure shown in FIG.4, that is, in such a direction that the bending of the honeycombstructure composed of graphite layers may be occurred. However, sincethe graphite layer itself is resistant to a force in such a directionthat the layer plane is stretched, even when the vending thereof isincreased, it may not develop into the breaking up of such athree-dimensional structure as shown in FIG. 4. Thus, such a materialthat can flexibly respond to a given direction and can be stronglyresistant to another direction, particularly to a compressing force, maybe applied as a coating material.

INDUSTRIAL APPLICABILITY

In a nanosize three-dimensional structure of carbonaceous materialaccording to the present invention, there is provided athree-dimensional structure where, instead of stacking graphite films ina layered shape, a plurality of graphite layers are mutually in contactat an off-angle from parallel arrangement and at the site for thecontact, covalent bonds between carbon atoms take shape. Thethree-dimensional structure can produce a material having a lighterweight and a comparable or higher strength in comparison with aconventional nano-carbonaceous material, and has advantages that it isapplicable for a wide variety of uses such as composing material for amolecule/atom adsorbing structure, an electronic device and areinforcing material, which material may fulfil its function steadilyunder severe conditions (for instance, under a high temperature or astrain field being initiated). In particular, it can smash a curvaturelimit for bending a graphite layer plane in a conventional graphite-likenano-structure of carbonaceous material, resulting in improvement in acapacity to physically adsorb, for example, molecules.

1. A carbonaceous three-dimensional structure which is athree-dimensional structure made of carbonaceous material comprising aplurality of graphite-layer-like layer planes that are composed of ahexagonal network structure made up carbon, wherein the plurality ofgraphite-layer-like layer planes are arranged such that they mutuallyintersect or are in contact with each other; and at the sites for thecontact between the plurality of layer planes, there are alignedconnections via carbon-carbon covalent bonds in the shape of across-line.
 2. The structure as claimed in claim 1, wherein thecross-line formed at the sites for the contact between the plurality oflayer planes where there are aligned connections via carbon-carboncovalent bonds constructs a straight or curved line.
 3. The structure asclaimed in claim 1, wherein as the sites for the contact between theplurality of layer planes where there are aligned connections viacarbon-carbon covalent bonds, there is at least one structure wherethree or more surfaces of the graphite-layer-like layer planes arearranged so as to mutually intersect or are in contact with each otheron the same cross-line.
 4. A carbonaceous three-dimensional structurewhich is a three-dimensional structure made of carbonaceous materialcomprising a plurality of graphite-layer-like layer planes that arecomposed of a hexagonal network structure made up of carbon, wherein theat least two graphite-layer-like layer planes are non-parallel graphitelayer planes and have such a structure that the site for the contacttherebetween forms a straight crease.
 5. The structure as claimed inclaim 4, wherein among the plurality of graphite-layer-like layer planesincluding the at least two graphite-layer-like layer planes of which thesite for the contact forms a straight crease, the at least twographite-layer-like layer planes forming the straight crease and atleast one additional graphite-layer-like layer plane have such aconfiguration as to mutually cross or be in contact with each other onthe same cross-line.
 6. A carbonaceous three-dimensional structure madeof carbonaceous material comprising a plurality of graphite-layer-likelayer planes that are composed of a hexagonal network structure made upof carbon, wherein the structure comprises at least a frame composed ofsome of or all of the three-dimensional structures as claimed in claim 1concurring in compositive manner.
 7. A method of using the carbonaceousthree-dimensional structure as claimed in claim 1, wherein thecarbonaceous three-dimensional structure is used to form a molecule/atomadsorbing material.
 8. A method of using the carbonaceousthree-dimensional structure as claimed in claim 1, wherein thecarbonaceous three-dimensional structure is used to form an electronicdevice having at least three terminals.
 9. The method for using acarbonaceous three-dimensional structure according to claim 8, whereinsaid electronic device having at least three terminals is a transistor.10. A method for using the carbonaceous three-dimensional structure asclaimed in claim 1, wherein the carbonaceous three-dimensional structureis used to form a reinforcing material.
 11. A process for constructing acarbonaceous three-dimensional structure made of carbonaceous materialcomprising a plurality of graphite-layer-like layer planes that arecomposed of a hexagonal network structure made up of carbon, whereinsaid three-dimensional structure is the carbonaceous three-dimensionalstructure as claimed in claim 1; and the process comprises the steps of:producing graphite-layer-like fragments having a hexagonal networkstructure made of carbon; and forcing the graphite-layer-like fragmentsproduced thereby into coming into collision with each other.
 12. Theprocess as claimed in claim 11, wherein in the step of forcing thegraphite-layer-like fragments, at least two fragments are impacted toeach other in an arrangement that the fragments mutually cross or are incontact with each other at an inter-plane angle between thegraphite-layer-like fragments to be in collision showing substantiallyother than 180°.
 13. A carbonaceous three-dimensional structure which isa three-dimensional structure made of carbonaceous material comprising aplurality of graphite-layer-like layer planes that are composed of ahexagonal network structure made up of carbon, wherein the structurecomprises at least a frame composed of some of or all of thethree-dimensional structures as claimed in claim 4 concurring incompositive manner.
 14. A method of using the carbonaceousthree-dimensional structure as claimed in claim 4, wherein thecarbonaceous three-dimensional structure is used to form a molecule/atomadsorbing material.
 15. A method of using the carbonaceousthree-dimensional structure as claimed in claim 4, wherein thecarbonaceous three-dimensional structure is used to form an electronicdevice having at least three terminals.
 16. The method for using acarbonaceous three-dimensional structure according to claim 15, whereinsaid electronic device having at least three terminals is a transistor.17. A method for using the carbonaceous three-dimensional structure asclaimed in claim 4, wherein the carbonaceous three-dimensional structureis used to form a reinforcing material.
 18. A process for constructing acarbonaceous three-dimensional structure made of carbonaceous materialcomprising a plurality of graphite-layer-like layer planes that arecomposed of a hexagonal network structure made up of carbon, whereinsaid three-dimensional structure is the carbonaceous three-dimensionalstructure as claimed in claim 4; and the process comprises the steps of:producing graphite-layer-like fragments having a hexagonal networkstructure made of carbon; and forcing the graphite-layer-like fragmentsproduced thereby into coming into collision with each other.
 19. Theprocess as claimed in claim 18, wherein in the step of forcing thegraphite-layer-like fragments, at least two fragments are impacted toeach other in an arrangement that the fragments mutually cross or are incontact with each other at an inter-plane angle between thegraphite-layer-like fragments to be in collision showing substantiallyother than 180°.
 20. A method of using the carbonaceousthree-dimensional structure as claimed in claim 6, wherein thecarbonaceous three-dimensional structure is used to form a molecule/atomadsorbing material.
 21. A method of using the carbonaceousthree-dimensional structure as claimed in claim 6, wherein thecarbonaceous three-dimensional structure is used to form an electronicdevice having at least three terminals.
 22. The method for using acarbonaceous three-dimensional structure according to claim 21, whereinsaid electronic device having at least three terminals is a transistor.23. A method for using the carbonaceous three-dimensional structure asclaimed in claim 6, wherein the carbonaceous three-dimensional structureis used to form a reinforcing material.
 24. A process for constructing acarbonaceous three-dimensional structure made of carbonaceous materialcomprising a plurality of graphite-layer-like layer planes that arecomposed of a hexagonal network structure made up of carbon, whereinsaid three-dimensional structure is the carbonaceous three-dimensionalstructure as claimed in claim 6; and the process comprises the steps of:producing graphite-layer-like fragments having a hexagonal networkstructure made of carbon; and forcing the graphite-layer-like fragmentsproduced thereby into coming into collision with each other.
 25. Theprocess as claimed in claim 24, wherein in the step of forcing thegraphite-layer-like fragments, at least two fragments are impacted toeach other in an arrangement that the fragments mutually cross or are incontact with each other at an inter-plane angle between thegraphite-layer-like fragments to be in collision showing substantiallyother than 180°.